JERUSALEM (JTA) — Israel’s Health Ministry will inoculate about 200,000 children with a weakened, live form of the polio virus in an effort to prevent the spread of the disease after its discovery in wastewater.

The announcement of the campaign on Sunday comes in response to the discovery in May of the polio virus in wastewater in Israel’s South that reportedly had been there since February.

Children up to age 9 will be inoculated with the vaccine. The children already have been inoculated against polio in their regular childhood vaccinations.

The purpose of the extra vaccine is to pass the weakened virus to adults with whom the children come into contact who may not previously have been vaccinated.

Israel’s Health Ministry has ordered half a million doses of the live weakened vaccine, and has taken delivery on 200,000 doses, which were distributed Sunday to clinics in the South.

There is a less than one in a million chance that an adult exposed to the vaccine will develop the disease.

Across Israel, the vaccination rate against polio is 94 percent, according to the World Health Organization, which is supporting the vaccination campaign and whose representatives reportedly called it “necessary.”

After being detected in May, the virus was detected in samples from at least 10 sites in Israel, mostly from the southern part of the country, according to WHO. In July, the virus also was found in sewage systems in Ramle, Lod, Modi’in and communities in the center of the country.

It is believed the virus was brought to Israel from Egypt; polio was discovered in sewage in Egypt in December. The same virus also is prevalent in Pakistan.

Israel experienced its last case of polio in 1988.

WHO sent a delegation to Israel in recent weeks to investigate the situation. There is concern in Europe that the disease will spread from Israel to other countries.